You could always do this with contact lenses, so meh.
Yes, you can. But, be sure to get them from a reputable source.
I read an article last week about "cosmetic" contact lenses that were popular accessories for costumes. There are tinted ones and even ones with designs. Here's an example:
The problem? Contacts should be fitted to your eyes by an optometrist. If you get one that doesn't fit, it can do serious damage to your eyes.
I found the article, but it was reprinted in a lot of places. Google for "Laura Butler contact lens" without the quotes.